Speaking Tuesday as the white paper was released, officials said China and other developing countries had taken serious steps while developed countries lagged. Xie Zhenhua, the head of the Chinese delegation to the Durban meeting, said poorer countries accounted for 57 percent of emission reductions.

“We hope nations of the world translate their political willingness into concrete actions,” Mr. Xie said at the news conference.

The report said that China achieved a 20 percent reduction in carbon emissions between 2005 and 2010 and planned to cut another 17 percent by 2015. The reduction is per unit of gross domestic product, the most common measurement of economic output. This means that while China’s overall carbon emissions will rise along with its economic output, its industries will become more efficient.

China expects developed countries under the protocol to clarify their quantities for emissions reductions under the second commitment period during the Durban conference, while those not covered by the accord should pledge comparable targets, Xie said. “Developing countries should make voluntary emission-reduction commitments.”

Under Kyoto’s first enforcement period, 35 nations and the European Union committed to cut emissions by a collective 5.2 percent from the 1990 levels by 2012.

Some nations are turning down the extension of the protocol to emphasize “environmental integrity,” Xie said. “This is an excuse as most of the countries have made commitments after the Copenhagen talks” in 2009.